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L. o. BALDWIN & J. 0. THURSTON.

INSULATOR FOR TELEGRAPH WIRES No. 297,101.

r nu Patent UNITED STATES PATENT OFFICE.

LUTHER O. BALDWIN AND JOHN G. THURSTON, OF MANCHESTER, N. H.

lNSULATOR FOR TELEGRAPH-WIRES.

SPECIFICATION forming part of Letters Patent No. 297,101, dated April22. 1884.

Application filed October 18, 1883. (No model.)

New Hampshire, have invented a new and useful Improvement in Insulatorsfor Telegraph-WVires, of which the following is a specification.

Our invention relates to improvements in insulators for telegraph-wires,in which the insulator is connected to the bracket-pintle orsupporting-pin by partially turning the insulator after thesupporting-pin is inserted therein, instead of by means ofscrew-threads.

The object of our invention is to provide means for preventing theinsulator from being turned 'on its supporting-pin when they are puttogether for use.

Our invention consists in a cup of some non-conducting material,preferably glass, having its interior shaped to receive thesupporting-pin, in combination with a pin adapted to be inserted andturned, and then farther inserted to lock and form a firm bearing forthe inverted cup, substantially as hereinafter fully described,reference being had to the accompanying. drawings, in which- Figure l isan elevation, with the insulatingcup in section, showing the pininserted as far as it will go without being partially turned. Fig. 2 isa similar view, showing the pin in place, and so looking the cup as toprevent its being withdrawn without first partially separating the cupand pin, and partially turning one on the other. Fig. 3 is alongitudinal cross-section through the insulating-cup; and Fig. 4 is abottom view of the insulating-cup.

The best way now known to us for carrying out our invention is to turn aknob or bulge, a, on the top of the pin A and make two sides of thisknob fiat. Turn the pin from the knob to near the lower part, a, to atapering form. The diameter of this tapering part at a in Fig. 2 isgreater than the longest diameter of the knob a. The lower part, a, ofthe pin is made either in the usual round form or in a bracket shape forinserting into a hole or for being spiked to a post.

The upper part, b, of the interior of the insulating-cup B is made tofit snugly the up per end, a, of the pin A-that is, it is made into ashallow chamber having two straight sides and round'ends. This chamberis best movement.

determines the distance the insulating cup may be moved on the pin by anupward strain before the knob in the pin arrests its further Just belowthe chamber 1) a circular chamber, 1), is made, its diameter and depthbeing such as to allow the knob a to turn in it. Below the chamber 1)the interior of the cup is made oval at b the shorter diameter oftheoval being the same as the diameter of the tapering part of the pinat the line a in Fig. 2, and the longer diameter being slightly greaterthan the longest diameter of the knob a. on the pin A. The oval shape atb expands gradually until it forms a circle at b", the diameter of whichis the same as thediameter of the tapering part of the pin at a in Fig.2, which, as above stated, is slightly greater than the longest diameterof the knob a. This shape gives the cup a firm bearing on the pin at aand causes a partial contact between the two up to a when-the pin is inplace, as shown in Fig. 2.

The manner of inserting the pin will be readily understood by referringto Fig. 1, in which it is shown in the position to allow the knob a topass through the oval-shaped part of the cup, and the knob having passedthis part and ready to be turned in the circular chamber 1/ before beingpushed up into the chamber 1), the straight sides of which prevent thecup from turning on the pin.

We claim as our invention- 1. A cup of non-conducting material havingits interior shaped substantially as described, in combination with apin which, when partially inserted, allows the cup to turn, and whenfully inserted forms a bearing for and prevents the cup from turning,substantially as set forth.

2. A cup of non-conducting material having its interior formed into anupper chamber with flat sides, a middle circular chamber, and a lowertapering chamber oval at one end and circular at the other, incombination with a supporting-pin having a knob with flat sides at oneend, its other end adapted to be secured to an arm or post, and acylindrical tapering part between these ends, substantially as and forthe purpose set forth.

LUTHER O. BALDWVIN. JOHN G. THURSTON.

Witnesses:

W. A. COPELAND,

55 made as shallow as possible, since its depth l G. B. MAYNADIER.

